Bug 700908 - Validate matching rules when creating a new attribute
    
    The panel used to create and edit custom attribute definitions was
    only validating the matching rule selections when an editing an
    existing attribute.  No validation was being done when creating a
    new attribute.
    
    The problem was that the code that checks if the matching rule
    combo boxes are dirty is only executed when editing an existing
    attribute (all values are dirty when creating a new attribute).
    The validation code was lumped in with this same code, so it was
    also only being executed when editing an existing attribute.  This
    patch causes the validation to be done when creating new attributes
    as well as editing them.